Microphone amplifier



April 1941- .w. A. ZARTH 2,239,308

MICROPHONE AMPLIFIER Filed April 1, 1940 19 2F INVENTOR Mizamfl Zdrf/n I Patented Apr. 22, 1941 MICROPHONE AMPLiFIER William A. Zarth, Jamaica, N. Y., assignor to Dictograph Products Company, Inc., New York, N. Y., a corporation of Delaware Application April 1, 1940, Serial No. 327,141

6 Claims.

This invention relates to hearing appliances and relates particularly to improvements in microphonic or mechanical amplifiers for hearing aid devices.

Microphonic or mechanical amplifiers usually consist of a carbon granule microphone having spaced diaphragms and interposed carbon granules which form an electric path of variable resistance through which current is supplied from a battery to an audiphone. One or both of the diaphragms may be vibrated, by means of an electromagnet through the medium of electrical current supplied by the battery and controlled by a transmitter or microphone, to cause a variation in resistance of the carbon granule microphone.

The most serious disadvantage of such amplihers is that a change of the position of the microphone button beyond certain limits will cause the carbon granules to be displaced out of 1 contact with the diaphragm, thereby changing the resistance of the amplifier and sometimes rendering it completely incapable of transmitting current.

Various attempts have been made to overcome this defect of such amplifiers, such as, for example, by providing conical or otherwise nonplanar diaphragms. This expedient is effective, but the diaphragms are expensive and due to their peculiar shape necessitate a considerable alteration in the microphone construction.

It has been suggested also that more satisfactory operation could be obtained by arranging the diaphragms of an ordinary microphone button at right angles to the wider face of a flat battery to which the amplifier is attached so that the proper relationship between the diaphragms and the carbon granules can be maintained when the battery is lying on one of its fiat faces or is in an upright position. While this expedient is eiiective under the conditions mentioned above, it has been observed that the battery is not by any means limited to these positions; in fact, more often than not the battery is disposed in an angular position, thereby displacing the carbon granules and rendering the booster ineffective or inefiicient.

An object of the present invention is to overcome this disadvantage of the prior constructions by providing microphonic or mechanical amplifiers which are effective in substantially all angular positions of the battery to which they are attached as well as when the battery is disposed in a horizontal or vertical position.

Other objects of the invention will become apparent from a description of a typical form of microphoni'c or mechanical amplifier embodying the invention.

Microphonic amplifiers or boosters of .the type embodying the present invention are characterized by a supporting element or casing which may be attached to the narrow end of a flat battery and which supports a carbon granule microphone having diaphragrns or conducting plates which are vertically disposed in an upright position of the battery and are inclined at angle of less than 90 and preferably about 45 to the wide faces or sides of the battery.

The casing or supporting plate may be provided with suitable plugs which are receivable in sockets in the battery so that the booster or mechanical amplifier forms, in effect, a continuation from the end face of the battery.

With this construction .the diaphragm plates will be vertically disposed when the battery is in an upright position, but will be inclined at an acute angle to the horizontal when the battery is disposed horizontally. The inclination of the plates is such that adequate contact between them and the carbon granules 'therebetween is obtained when the battery is in a horizontal or vertical position. Moreover, even when the battery is lying non-horizontally or inclined with respect to the horizontal, the inclination of the plates is such as to maintain the necessary contact between them and the interposed carbon granules. Thus, When the battery is placed in the hip pocket, a quite common place for such batteries to be carried, the microphone button can be turned and twisted in various planes due to movements of the wearer without causing the carbon granules to lose contact with the plates. If, in certain positions of the wearers body, the plates of the microphone should by chance be disposed substantiaiiy horizontally, this can be overcome by merely shifting the battery to the other hip pocket, thus disposing the microphone at about a right angle to its former position and producing the desired contact between the plates and the carbon granules.

For a better understanding of the present invention, reference may be had. to the accompanying drawing, in which:

Figure 1 is a view in vertical section of a typical form of microphone amplifier supported on the end of a battery which is partiy broken away; and

Figure 2 is abottom view of the microphone with the base plate removed therefrom.

The form of the amplifier illustrated in Figures 1 and 2 of the drawing may include a base plate l having suitable contact plugs H and I2 mounted therein which are adapted to be received in suitable sockets l3 and It in the end of a flat battery l5 so that the base plate may be readily attached and detached from the battery.

The base plate it? serves to close the bottom of a hollow casing 15, a generally rounded construction including a curved end ll, flat side walls It and I9 and an opposite inclined end iii]. The inclined end of the housing is provided with a plurality of contact-plug receiving apertures 2| by means of which the connection plugs of a transmitter and a receiver may be connected to the amplifier.

Within the casing it is disposed a microphone button 22 which is disposed at about a angle to the major axis of the casing l6 and perpendicular to the base plate It]. The microphone button 22 may be of conventional construction including an electromagnet E for vibrating a conducting plate or diaphragm D spaced from a relatively stationary diaphragm or conducting plate D. Carbon granules C are interposed in the space between diaphragm D and plate D. The microphone button 22 is retained in its angularly disposed position by means of lugs or projections 23, 24 and 25 having inclined faces on the interior of the casing it which engage surfaces of the button 22 and prevent it from rotating relatively to the casing,

The connections between the battery, the transmitter (not shown) and the audiphone (not shown) are as follows: the plug H is connected by means of a resilient contact plate 25 to a metallic ring 2? forming the major portion of the casing of the microphone button 22 and which is electrically connected to the plate D therein. The contact button 23 at the right hand end of the microphone, as viewed in Figures 1 and 2, is insulated from the ring 27 and electrically connected to the plate D and through the interposed carbon granules C to the plug H. A suitable spring contact 29 fixed to the casing l6 engages the contact button 23 and is provided with a spring tongue 3-8 which engages one contact plug connected to an audiphone, thus forming one side of a circuit between the battery and the audiphone.

The other side of the battery is connected by means of the plug E2 to a spring contact Sl engaging a contact button 32, and by means of a conducting strip 33 to a U-shaped contact element 34 mounted on the inner surface of the inclined portion 26 of the casing. The U-shaped contact 34 connects to the other side of the audiphone, thus completing the circuit through the battery, the amplifier microphone and the audiphone. The contact 34 also is connected to one side of the transmitter.

The other side of the transmitter is connected by means of a contact 8:": mounted on the casing I 5 to one contact $6 of the electromagnet E in the microphone button 22 and through the electromagnet to the ring 27 of the microphone button 22 by means of a conducting spring 31. The above connections provide a double circuit through the transmitter, the amplifier and the audiphone whereby current is supplied to the electromagnet and to the amplifier and audiphone by the battery l5.

With an amplifier of this type disposed on the end of a fiat battery, it will be apparent that when the battery is in an upright position, the carbon granules C will be brought into uniform contact with the plates D and D of the button 22, by reason of the vertical disposition of the plates. Moreover, when the battery is laid on its flat side and the amplifier is in the position shown in Figure 2, the carbon granules C will drop down toward the lower ends of the plates D and D and will maintain contact between them. When the amplifier is rotated clockwise through 45, the plates of the microphone button 22 will be disposed perpendicularly and upon rocking the de vice still another 45 clockwise, adequate contact between the carbon granules C and the plates D and D will still be maintained. It will be apparent, therefore, that the amplifier is capable of r a wide latitude in its position while still maintaining satisfactory engagement between the carbon granules and the plates thereof. It is only when the button is disposed with the plates horizontally, or substantially so, that difiiculty will arise in the operation of the device and this can be readily overcome by merely shifting the amplifier to another pocket and thus rotating it through about From the foregoing description of the invention, it will become apparent that a very simple and effective construction has been provided for maintaining the proper operating relationship of a microphone amplifier.

While but a single form of invention embodying the invention has been described herein, it will be understood that the invention may take other forms and that variations in the details of the construction may be made without departing from the invention so long as the plates of the microphone button are inclined at an acute angle to the flat face of the battery. Therefore, the above described embodiment of the invention should be considered as illustrative only and not as limiting the scope of the following claims.

I claim:

1. In a microphonic amplifier, the combination of a microphone button having substantially flat parallel conducting plates and interposed granular conducting material, means for supporting said microphone button on an end of a thin battery having wide side walls with said plates extending longitudinally of said battery and inclined transversely of said battery at an acute angle to the side walls of said battery.

2. In an amplifier for hearing aid devices, the combination of a casing, conducting plugs projecting from the base of said casing and adapted to engage in sockets in the upper face of a thin battery having wide side faces, a microphone button within said casing having spaced cooperating substantially fiat conducting plates therein, operatively connected to said plugs, said plates being substantially parallel and inclined at an acute angle to the side faces of said battery.

3. In a microphonic amplifier, the combination of a casing, means for detachably connecting said casing to an end of a thin battery having substantially fiat wide side walls, a microphone button in said casing having substantially flat parallel conducting plates therein, means in said casing engaging said microphone button to maintain said plates inclined at an angle of about 45 with respect to said wide side walls and perpendicular to said end of said battery.

4. In a microphonic amplifier, the combination of an elongated casing having a substantially flat bottom adapted to be detachably connected to an end of a flat battery with the major axes of said casing and said end substantially parallel, and a microphone button having substantially diaphragm arranged at an acute angle to said flat wall.

6. In combination with a microphone button having a substantially flat diaphragm engaging granular conducting material and an electromagnet for vibrating the diaphragm, a flat walled support for said button adapted to be carried flatwise against the person, and means for connecting said button to said support with said diaphragm arranged at an angle of about 45 to said fiat wall.

WILLIAM A. ZAR'IH. 

